Update the buck installation documentation
Update the buck installation documentation

Instead of adding the buck build's output directory in the path, we
make a symbolic link to the executable from `~/bin`.

Instrutions for setting up ~/bin are copied from the repo installation
guide at Android [1].

The sections for Linux and Mac OS are merged to a single section, and
the summary now mentions that only Linux and Mac OS are supported.

[1] http://source.android.com/source/downloading.html

Change-Id: Iaa973ec4116b03371ea386e4286c8bbfa36e7190

joshuawilson/merrit,quyixia/gerrit,Team-OctOS/host_gerrit,supriyantomaftuh/gerrit,thesamet/gerrit,bpollack/gerrit,TonyChai24/test,thinkernel/gerrit,netroby/gerrit,joshuawilson/merrit,anminhsu/gerrit,netroby/gerrit,Distrotech/gerrit,Team-OctOS/host_gerrit,MerritCR/merrit,thinkernel/gerrit,supriyantomaftuh/gerrit,WANdisco/gerrit,TonyChai24/test,Saulis/gerrit,jackminicloud/test,quyixia/gerrit,dwhipstock/gerrit,gerrit-review/gerrit,thinkernel/gerrit,MerritCR/merrit,supriyantomaftuh/gerrit,supriyantomaftuh/gerrit,thesamet/gerrit,qtproject/qtqa-gerrit,gerrit-review/gerrit,renchaorevee/gerrit,gerrit-review/gerrit,supriyantomaftuh/gerrit,qtproject/qtqa-gerrit,GerritCodeReview/gerrit,bootstraponline-archive/gerrit-mirror,Saulis/gerrit,thesamet/gerrit,Saulis/gerrit,gerrit-review/gerrit,jackminicloud/test,joshuawilson/merrit,Saulis/gerrit,gracefullife/gerrit,midnightradio/gerrit,renchaorevee/gerrit,Overruler/gerrit,anminhsu/gerrit,hdost/gerrit,Overruler/gerrit,pkdevbox/gerrit,Saulis/gerrit,WANdisco/gerrit,Seinlin/gerrit,joshuawilson/merrit,supriyantomaftuh/gerrit,bpollack/gerrit,MerritCR/merrit,gcoders/gerrit,MerritCR/merrit,quyixia/gerrit,GerritCodeReview/gerrit,bpollack/gerrit,qtproject/qtqa-gerrit,renchaorevee/gerrit,thesamet/gerrit,anminhsu/gerrit,bpollack/gerrit,Overruler/gerrit,Seinlin/gerrit,jackminicloud/test,midnightradio/gerrit,Team-OctOS/host_gerrit,bpollack/gerrit,hdost/gerrit,hdost/gerrit,pkdevbox/gerrit,midnightradio/gerrit,hdost/gerrit,supriyantomaftuh/gerrit,WANdisco/gerrit,thesamet/gerrit,joshuawilson/merrit,netroby/gerrit,renchaorevee/gerrit,Seinlin/gerrit,TonyChai24/test,Overruler/gerrit,quyixia/gerrit,zommarin/gerrit,midnightradio/gerrit,pkdevbox/gerrit,jackminicloud/test,jackminicloud/test,gcoders/gerrit,WANdisco/gerrit,bootstraponline-archive/gerrit-mirror,anminhsu/gerrit,quyixia/gerrit,anminhsu/gerrit,qtproject/qtqa-gerrit,qtproject/qtqa-gerrit,thesamet/gerrit,zommarin/gerrit,midnightradio/gerrit,gerrit-review/gerrit,WANdisco/gerrit,bpollack/gerrit,TonyChai24/test,qtproject/qtqa-gerrit,dwhipstock/gerrit,GerritCodeReview/gerrit,Distrotech/gerrit,dwhipstock/gerrit,TonyChai24/test,gcoders/gerrit,Team-OctOS/host_gerrit,thinkernel/gerrit,MerritCR/merrit,gracefullife/gerrit,TonyChai24/test,joshuawilson/merrit,quyixia/gerrit,GerritCodeReview/gerrit,zommarin/gerrit,Distrotech/gerrit,Team-OctOS/host_gerrit,pkdevbox/gerrit,qtproject/qtqa-gerrit,quyixia/gerrit,Seinlin/gerrit,GerritCodeReview/gerrit,gcoders/gerrit,pkdevbox/gerrit,GerritCodeReview/gerrit,netroby/gerrit,Distrotech/gerrit,TonyChai24/test,pkdevbox/gerrit,renchaorevee/gerrit,WANdisco/gerrit,gerrit-review/gerrit,thinkernel/gerrit,WANdisco/gerrit,netroby/gerrit,joshuawilson/merrit,MerritCR/merrit,Team-OctOS/host_gerrit,netroby/gerrit,thinkernel/gerrit,anminhsu/gerrit,dwhipstock/gerrit,Seinlin/gerrit,Overruler/gerrit,hdost/gerrit,bootstraponline-archive/gerrit-mirror,Distrotech/gerrit,zommarin/gerrit,gracefullife/gerrit,hdost/gerrit,renchaorevee/gerrit,jackminicloud/test,bootstraponline-archive/gerrit-mirror,dwhipstock/gerrit,Seinlin/gerrit,Team-OctOS/host_gerrit,MerritCR/merrit,Distrotech/gerrit,MerritCR/merrit,gcoders/gerrit,Seinlin/gerrit,gcoders/gerrit,joshuawilson/merrit,bootstraponline-archive/gerrit-mirror,Saulis/gerrit,midnightradio/gerrit,Distrotech/gerrit,GerritCodeReview/gerrit,gcoders/gerrit,gracefullife/gerrit,dwhipstock/gerrit,gerrit-review/gerrit,thinkernel/gerrit,gracefullife/gerrit,anminhsu/gerrit,hdost/gerrit,GerritCodeReview/gerrit,pkdevbox/gerrit,renchaorevee/gerrit,thesamet/gerrit,bootstraponline-archive/gerrit-mirror,dwhipstock/gerrit,zommarin/gerrit,Overruler/gerrit,netroby/gerrit,jackminicloud/test